Sound-reproducing method and apparatus



Aug. 14, 1928.

G. RAMSEY SOUND REPRO DUCING METHOD AND APPARATUS Filed April 21, 1924Amplifier 2 Sheets-Sheet 2 E INVENTOR i Patented Aug. 14, 1928.

UNITED STATES i enema amuse V new roan.

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Application lilcd April er, 1924. Serial No. $027,863-

This invention relates to translating methtranslated. Also these priorart devices reods and apparatus, and particularly to methquire a fairlylarge number of parts, includods and apparatus for translatingelectrical ing one or more electromagnets having a undulations orimpulses into corresponding large number of turns. 5 sound undulationsor impulses. ln accordance with the foregoing and The general objects ofthe invention are other objects of the present invention these toprovide a method of and to provide an difliculties of the prior art maybe overcome apparatus for translating electrical undulaby modulating asuperaudible frequency curtions directly into sound undulations. rentWith the undulations to be translated 10 Another object of the inventionis to proand passing this modulated current across a vide a translatingdevice free of moving spark gap positioned in an air pocket which parts.may be in communication with the small end Other and important objectsof the invenof a suitable horn or the like. Due to the tion are toprovide a method of and to provariations in the dynamic action of thespark 15 vide an apparatus for subjecting air to the and the variationsin the instantaneous rate action of electrical undulations to produce ofheating of the air in the pocket, the colsound Waves corresponding tothe electrical umn of air inclosed in the horn is set into undulations.corresponding vibration. If the carrier cur- Other objects of theinvention are to prorent is unmodulated the only vibration pro- 20 videa method of and to provide an appaduced is of superafidible frequency,and ratus for translating electrical undulations hence no sound isproduced, i. e., the column into corresponding sound undulations by ofair in the horn is vibrated at a frequency varying the intensity of anelectrical diswhich is superaudible. However, when the charge in air inaccordance with the electricarrier current is modulated with the audible25 cal undulations. frequency undulations which are to be trans- Amongthe more specific objects of the lated into sound waves, the intensityof the invention are to provide a method of and spark is varied inaccordance with these un to provide an apparatus for translatingaudulations and hence corresponding vibration dible frequency electricalundulations into of the air column enclosed by the horn is wcorresponding sound undulations by moduproduced. ln other Words, thesuperaudible lating a superaudible frequency electric curfrequencyvibration of the air column in the rent in accordance with theundulations to be horn is modulated at audible frequency thustranslated, passing the modulated current producing a sound whichcorresponds to the across a spark gap, and subjecting the atmodulation.

35 mosphere to the efiect oi the variations in In order to keep thepocketed air at suitintensity of the superaudible frequency elecabletemperature under continued operation trio spark. of the apparatus thewall surrounding the ln the prior art electrical undulations or airpocket may be made of a good heat conimpulses have generally beentranslated into ducting material, blackened and provided sound wavesthrough the instrumentality of with suitable fins to increase radiationof mechanical moving arts such as a diaheat. The electrodes which formthe spark phragln or the like w ich acts upon the atgap may beadjustable to vary the length mosphere and is electromagneticallvibratofthe spark, and preferably both electrodes ed in response to theelectrical und ations to are adjustable so that the length of the spark45 be translated. Withsuch devices it has been may be varied withoutshifting the position dificult to obtain accurate or undistorted of thecenter of the spark with respect to the translation on account of theinertia of the Walls of the air pocket. diaphragm and the fact that inmost cases Figure .1 of the drawings shows a radio the diaphragm has anatural period or pereceiving circuit embodying the invention. 50 riodsof vibration, all of which render it Figure 2 is a time diagram showingan ildificult if not impossible to make a dialustrative current wavedelivered'by the dephragm move accuratel in accordance with tector ofthe circuit shown in Figure 1. 105 the variations in the electriccurrent to be Figure 3 is a time diagram illustrating the carriercurrent of the sending or oscillating unit of the circuit shown in igure1.

Figure 4 is a time diagram illustrating the current delivered to thetranslating device by the circuit shown in Figure 1.

Figure 5 is an alternative radio receivin circuit embodying theinvention. a

Figure 6 is a fragmentary sectional view showmg the translating device.

Figure 7 is an elevational view showing the mounting of a horn embodyinga translating device in accordance with the present invention.

It is realized that the present invention may be practiced in formsother than those herein illustrated and described, and hence it isdesired that the present disclosure be considered as illustrative andnot in the limiting sense.

- circuit 1 is arranged-to be excited by radio waves and tocorrespondingly energize an amplifying and detecting unit 2, which maybe of any suitable and well known type. An oscillator or other-suitablecontinuous wave sending unit 3, which produces a carrier such as shownin Fig. 3, is connected in any suitable manner to be modulated by thecurrent delivered by the amplifier-detector unit 2. As is wellunderstood in the art the detector current has a wave form such as shownin Figure 2 and modulates the carrier of the sending unit 3, causingthat unit to deliver a current of the form shown in Figure 4. Thevoltage at which the current is delivered by the sending unit 3 may hestepped up by means of a suitabletransformer 4, after which it isdischarged across spark gap 5 positioned in air pocket 6. As shown byFigure 4 the amplitude of this current varies in accordance with theaudible frequency undulations delivered by the amplifier detector unit,and hence the rate at which energy is liberated by the spark within theair pocket varies accordingly. The energy liberated at the spark gap islargely in the form of heat, resulting in expansion and contracting ofthe pocketed air in accordance with the form of the current shown inFigure 2. This action is probably aided by the variations in the dynamicaction of the spark. The air pocket being in communication with theouter air, a sound is produced which'corresponds to the electricalundulations of Figure 2.

The sending unit 3 may be operated to generate a carrier current of anysuitable superaudible frequency, and a frequency may be selected whichpermits the design of a high efficiency circuit, and the use of an ironcore transformer at 4, if desired. If desired the secondary oftransformer 4 may be tuned by closing switches 7 and 8, thus connectingit across variable condenser 9.

The apparatus is preferably operated so that the carrier of the unit3 isonly partially modulated as shown in Figure 4, this insuring that thepotential delivered to the spark gap will always be sufiicient tomaintain the spark.

In the form of apparatus shown in Figure 5 an oscillatory circuit 10 isarranged to be excited by radio waves and to correspondingly energize anamplifier 11 of suitable type. The voltage at which the output of theamplifier is delivered may he stepped up by means of a suitable transformer 12, after which the current is passed between the electrodes ofspark gap 13. If desired, switches 14 and 15 may be closed to permit thesecondary of transformer 12 to be tuned by condenser 16. The heating anddynamic actions within the air pocket are independent of the directionin which the current flows between the electrodes of the spark gap 13,and hence no detector need be associated with the amplifier 11.

Referring to Figure 6, an air pocket denoted in general by 20 is formedby a spherical Wall 21 having integral heat radiating fins 22. The wall21 and fins 22 may be made of suitable heat conducting material such ascopper and may be blackened to increase the rate of radiation.Electrodes 23 and 24 are slidably mounted in insulating bushings 25 and26 respectively, thereby forming an adjustable spark gap within the airpocket 20. In order to insure proper cooling of the electrodes, thebush- -ings 25 and 26 may be made of material which is a good heatconductor as well as an insulator. A horn 27 in communication with the.air pocket as shown, may be integral with the walls 21 and may be of anyshape desirable from the standpoint of acoustical efficiency.

Referring to Figure 7, the horn 27 is supported by a base 28 whichincloses the air pocket, but is provided with suitable apertures 29 toavoid interference with the radiation of heat from the air pocket.Suitable means such as binding posts 30 and 31 are provided for makinthe necessary electrical connection to the e ectrodes of the spark gap.

From the foregoing description it is seen that a method and apparatushave been provided by which electrical undulations may be directlytranslated into corresponding sound waves, that diaphragms or othermoving parts have been-completely eliminated, and that a translatingdevice of exceedingly simple construction has been produced. It is alsoapparent that a method and apparatus have been provided whereby a.modulated superaudible frequency current may be translated intocorrespondmg sound waves without the necessity of rectification of thecurrent before translation. -The invention has been disclosed as appliedto radio receiving apparatus, but it will be apparent that it may beapplied in many other connections where it is desired to translateelectrical undulations into corresponding sound Waves.

Taving thus described my invention, what it claim is z-- l. The methodof reproducing sound which comprises producing an electrical sparlr by asuperaudible frequency current and modulating the spark current with anaudible frequency current.

2. The method of reproducing sound which comprises forming'a series ofsparks at superaudible frequency in air with a current modulated inaccordance with the sound to be reproduced.

3. The method of producing sound which comprises subjecting pocketed airto the action of a continuous series of electrical sparhs modulated withan audible frequency current.

an The method of reproducing sod i which comprises subjecting poclretedair to the action of a continuous series oi electrical sparlrs andmodulating the sparlr current with current corresponding to the sound tobe reproduced,

5. The method or producing sound which comprises subjecting oclreted airto the action out a superaudi is frequency spark and modulating thespark current with an audible frequency current.=

d. The method of reproducing sound which comprises subjecting ochetedair to the action oi a superaudible equency sparlr and modulating-thespark current with current corresponding to the sound to be reproduced,

it The method of reproducing sound which comprises subjecting pocketedair to the action of a spark and modulating the spark in accordance withthe sound tohe reproduced 8. The method of reproducing sound whichcomprises producing a spark with superaudible frequency current andmodulating the superaudible frequency current with an electricalpulsation of an audible so rate.

9. The method of reproducing sound which comprises producing a sparkwith superaudible llrequency current andmodulatiug said current withdetec radio signals,

ill. it sound reproducing system comprising a sparlr gap electricalmeans connected to said sparl: gap to produce a superaudible frequencyspark, and means to modulate said spark an audible frequency current,

Jill. A sound reproducing system comprising a spark gap, a closure atleast partially enclosing said sparlr gap, means connected said gap toproduce superaudible lirequency sparlr, and means to modulate saidsparlr with an audible frequency current.

1%.. ll. sound reproducing system oompris ing a sparh gap, electricalmeans connected dill ill

to said gap to produce a superaudible l'requency sparlr, and means tomodulate said sparh with a Varying current corresponding to a somid tobe reproduced iii. A sound reproducing system comprisinp; a spark gap,and electrical means con nected to said spark gap to produce asuperaudible frequency sport: modulated at an audible rate. r

M. A sound reproducing system comprising means to establish a col ol airmeans to vibrate said col of air at a lli. 7 od SOlllld. whic compriseselectrically producing directly in a r a superaudible frequency airvibration, and modulating the vibration at audible uenc freq y GEURGESEY.

